^That is up for debate as base 110 speed is a pretty high mark for either of the two to reach. And by convention, Electric types tend to have high speed. Not to mention that even if Reshiram is faster, it needs enough SpA to OHKO Latias/Latios through Soul Dew to avoid a likely OHKO on itself. To put this into perspective, 252 Hasty Lustrous Orb Palkia fails to OHKO 112/0 Latias with STAB Spacial Rend, and is OHKOd by a Dragon Pulse despite its 90/120 defenses. Physical Zecrom disregards Soul Dew completely which makes its job easier.
Skarm is debatable. Forretress is generally the better choice on teams that feature sun, as it is often used to spin for Ho-oh. Otherwise, Skarm's access to reliable Recovery, higher speed, and EQ immunity seem superior IMO. Thus, Reshi beats Forretress (sun), while Zekrom beats Skarm (Rain). But again, debatable.
Skarm is debatable. Forretress is generally the better choice on teams that feature sun, as it is often used to spin for Ho-oh. Otherwise, Skarm's access to reliable Recovery, higher speed, and EQ immunity seem superior IMO. Thus, Reshi beats Forretress (sun), while Zekrom beats Skarm (Rain). But again, debatable.